Head to their websites and watch their hands-on video review then.
Here's a video comparison with accompanying text between the 4S and the Galaxy S III. Good enough for you?
http://www.youtube.com/watch?v=MHUrE1mml4o
03:30 is where the fun begins. I dunno, looks just as smooth to me.
Don't get me wrong. I like the iPhone too, and I'm not the world's greatest Galaxy S III fan (I prefer my HTC One X tbh). But I'm not so blinded as to believe that a two year old phone, made by Apple or not, is any better.
Re: the quantitative/quantitative thing- your 'review' from that trusty bodybuilding blog isn't quantitative either, as I'm not seeing any FPS numbers quoted. These are all opinions. Having a video to actually see the performance for yourself, or better yet actually having the device in-hand, is the only way to make an accurate opinion for yourself.
And based on the numerous S IIIs I've used and reviews I've watched, none showed the performance to be 'far more laggy than an iPhone 4'.
If what you're saying is true, then like I said- it's a problem with the specific phone you were using rather than with the phone in general. Maybe he still had a whole bunch of applications still loaded up in the background. Who knows?
I hope you understand why I'm doubting you, seeing as how there are very few reviews or videos on the Internet that reflect your experience with the device while there are plenty showing the opposite.